For one group of children, the experimenter said: "I just found this toy!" As she brought out the toy, she pulled the first tube, as if by accident, and it squeaked. She acted surprised ("Huh! Did you see that? Let me try to do that!") and pulled the tube again to make it squeak a second time.
With the other children, the experimenter acted more like a teacher. She said, "I'm going to show you how my toy works. Watch this!" and deliberately made the tube squeak. Then she left both groups of children alone to play with the toy.
All of the children pulled the first tube to make it squeak. The
question was whether they would also learn about the other things the
toy could do. The children from the first group played with the toy
longer and discovered more of its "hidden" features than those in the
second group. In other words, direct instruction made the children less
curious and less likely to discover new information.
extracted from http://www.slate.com/articles/double_x/doublex/2011/03/why_preschool_shouldnt_be_like_school.html
extracted from http://www.slate.com/articles/double_x/doublex/2011/03/why_preschool_shouldnt_be_like_school.html